测试代码
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import com.jdbcutils.JDBCUtils;
public class JDBCDemo2 {
public void select(){
Connection conn = null;
PreparedStatement pstmt = null;
ResultSet rs = null;
try{
// 获取连接
conn = JDBCUtils.getConnection();
// 编写SQL:
String sql = "select * from user";
// 预编译SQL:
pstmt = conn.prepareStatement(sql);
// 获取结果集
rs = pstmt.executeQuery();
// 遍历
while(rs.next()){
System.out.println(rs.getInt("id")+" "+rs.getString("username")+" "+rs.getString("password")+" "+rs.getString("nickname"));
}
}catch(Exception e){
e.printStackTrace();
}finally{
// 关闭资源
JDBCUtils.release(rs, pstmt, conn);
}
}
}
package com.jdbcutils;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.Properties;
public class JDBCUtils {
private static final String driverClassName;
private static final String url;
private static final String username;
private static final String password;
static{
Properties Properties = new Properties();
try {
Properties.load(new FileInputStream("src/db.properties"));
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
driverClassName = Properties.getProperty("driverClassName");
url = Properties.getProperty("url");
username = Properties.getProperty("username");
password = Properties.getProperty("password");
}
//加载驱动
public static void loadDriver(){
try {
Class.forName(driverClassName);
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
//获取连接
public static Connection getConnection(){
Connection conn = null;
try {
loadDriver();
conn = DriverManager.getConnection(url, username, password);
} catch (Exception e) {
e.printStackTrace();
}
return conn;
}
public static void release(Statement stmt,Connection conn){
if(stmt != null){
try {
stmt.close();
} catch (Exception e) {
e.printStackTrace();
}
stmt = null;
}
if(conn != null){
try {
conn.close();
} catch (Exception e) {
e.printStackTrace();
}
conn = null;
}
}
public static void release(ResultSet rs,Statement stmt,Connection conn){
if(rs != null){
try {
rs.close();
} catch (Exception e) {
e.printStackTrace();
}
rs = null;
}
if(stmt != null){
try {
stmt.close();
} catch (Exception e) {
e.printStackTrace();
}
stmt = null;
}
if(conn != null){
try {
conn.close();
} catch (Exception e) {
e.printStackTrace();
}
conn = null;
}
}
}
db.properties
driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql:///web_test3
username=root
password=123
SQL建表语句
create database web_test3;
use web_test3;
create table user(
id int primary key auto_increment,
username varchar(20),
password varchar(20),
nickname varchar(20),
age int
);
insert into user values (null,'aaa','123','小丽',34);
insert into user values (null,'bbb','123','大王',32);
insert into user values (null,'ccc','123','小明',28);
insert into user values (null,'ddd','123','大黄',21);